What is reverb? A brief answer to this question will be given in this article. In its chapters, readers will find information about the devices with which you can get this effect, as well as about modern software used for this purpose.
Definition
So what is reverb?
In encyclopedic dictionaries one can find various definitions of this phenomenon. Their essence is approximately as follows. Reverb is a physical process that is considered in psychoacoustics and acoustics. It can be characterized as sound stability after its reproduction. A reverb is created when a sound or an electrical signal caused by it is reflected several times from something and then fades out.
It stops as it is absorbed by various surfaces in the immediate vicinity of it. Objects that “absorb” sound can be people, furniture, and so on. Air also has some absorption capacity. What is reverberation can be understood by pressing any piano key. The note is heard for some time after the person removed his hands from the instrument. That is, the sound source is silent, but its echo is still audible. It fades out gradually. This is reverb.
Math language
The characteristics of the reverb effect depend on some external circumstances. Its length or time is usually called the duration of sound stability from the moment the source is silent. This interval is measured in milliseconds.
Echo and Reverb
Often reverbs are confused with echoes. In fact, the first concept has a broader meaning. It also includes an echo, which can have a value from 50 to 100 milliseconds. The process discussed in this article is not limited to this scope. What is reverb? Speaking in the language of numbers, this is an aftertone, the duration of which can be lower than 50 milliseconds.
Where does reverb exist?
She appears not only in enclosed spaces. Its natural version can be heard in the forest, mountains, as well as in any territory where there are large or small objects that can reflect sound.
Reverb naturally occurs when a person speaks, sings, or plays an instrument.
Measurement standard
The reverberation time is, as already mentioned, the number of milliseconds during which the sound decays. It is measured from the moment the source completely subsides. When you want to determine its exact value, use a method called RT60.
This is an abbreviation for the English phrase reverberation time.
The number "60" indicates the number of decibels by which the sound volume should decrease. When this limit is reached, the time measurement ends.
Height dependent
Typically, the reverberation time is denoted by a single number, since it is not individual frequencies that are measured, but the whole sound. However, these parameters depend on each other. So, for greater accuracy, it is necessary to measure the attenuation time of the various frequencies that make up the sound. The upper range is known to have longer reverb. Low sounds, in contrast, subside faster. For this reason, it is better to make "multi-band" measurement, paying attention to each frequency separately.
Discoverer
At the end of the 19th century, American scientist Wallace Clement Sabin began work on sound research at Harvard University.
He conducted experiments to study the effect of the degree of absorption of various materials on the decay time of an echo. A physicist used an organ as a sound source. The stopwatch served as the measuring device.
The ears of the researcher himself were also of considerable importance, since in some cases it was by rumor that he determined the degree of note attenuation. Sabin measured the time required to lower the volume by 60 decibels. In his research, he came to the following results. The physicist found that the reverberation time is directly proportional to the size of the room. The larger the interior, the longer the note sounds.
An inverse relationship exists compared to the surface area of all objects capable of absorbing sound.
Optimal parameters
The ideal proportions of the room in which the music is played depend on the genre of the pieces. Each style uses a different reverberation time.
Halls designed for meetings, conferences, forums, lectures, and similar events where speakers are expected to speak to the public should have less reverberation. It is known that the excessive duration of the reflected sound reduces the clarity of speech, and therefore, can serve as an obstacle to its understanding. If one syllable continues to be heard while pronouncing the next, the phrase will be illegible. In this case, it will be difficult to understand what word was meant: cat, whale or code. On the other hand, if the reverberation time is too short, then the person’s voice or the sound of a musical instrument will lose some of its timbre. Music performed in a room with such a characteristic is not interesting to listen to. This will negatively affect the volume. Due to the jerky sound, the work will be perceived as too quiet.
The reverb effect is often used in recording studios in order to bring the desired color to musical compositions. With its help, you can achieve a richer and deeper flavor or, conversely, reduce the brightness of a particular party so that it does not drown out the others.
Based on the foregoing, it is possible to answer the question “what is reverberation” in the following way: this is one of the qualities of sound that is color and affects the perception of its listeners. However, a change in this indicator does not affect the height of the notes. The reverb of a room depends on its size and shape, as well as on the structure of the surface of the walls and other objects in it. Not the last role in this is played by building and finishing materials, or rather, their property such as density. It determines the ability to mute and reflect sound.
Reverb Measurement Methods
The first experiments on measuring the reverberation time were carried out using a graphic apparatus with a moving paper tape, on which the sound volume was recorded. As the oscillations damped, the device drew a curve that was a graph of this process. The sound for such studies needs quite loud and jerky. It should calm down instantly. Therefore, as a source, a gun loaded with blank cartridges or an inflatable ball, which burst from a needle and bursting and produced a characteristic cotton, was usually chosen.
Another way to measure the length of the reverb is to record the original sound and its echo after a certain period of time. Based on these data, the reverb length is calculated. This method has a definite advantage over the previously described. Sound recording can be made even in the hall before the concert, when all the spectators are already seated in their places.
To do this, just turn on the music and record it twice in this room.
Such a determination of the reverberation time for a particular hall will be the most accurate, since the number of spectators who come, the materials from which the clothes are sewn, and even the humidity on a particular day can affect the value of this indicator.
Artificial Reverb
Each sound engineer and producer knows how great the value of this sound parameter is to create a high-quality soundtrack that will be pleasant and interesting to listen to.
Vocal reverb creates a space effect that makes singing more “lively” and “realistic”. In the same way, you can achieve the presence of an echo effect in the recording.
The importance of giving the sound such characteristics when recording actors in the cinema cannot be overestimated. It is thanks to the excellent mastery of the sound engineer in the art of creating artificial reverberation of the voice that the viewer can transfer with the characters of the tape to a mountain cave or to the spacious halls of the royal palace.
Acoustic devices
One of the first methods to give the sound the desired reverb was to record simultaneously, made in close proximity to the source and at a certain distance from it. These two or more phonograms were superimposed on each other in the necessary proportions (with a certain volume). This method was also used when recording the song by David Bowie Heroes.
Electronic devices were invented to produce a similar effect. For example, in the studio Abbey Road used a reverb (the so-called apparatus for creating artificial aftertone and echo) based on a large vibrating metal plate. Guitar amplifiers still use devices whose main element is iron springs. This method of producing reverb was invented by Hamond, the creator of the famous electric organ.
There are many other devices for receiving reverb, all of them work according to their own original schemes.
Currently, digital effects are widely used, both made in the form of separate devices (pedals), and numerous computer programs.
Some people, on the contrary, are puzzled by the question of how to remove reverb. This may be necessary if, for example, a recording of an institute lecture made on a dictaphone is illegible. In this case, the Izotope Rx Dereverb program can help. But only those who have the skills to work in any of the sequencer programs (an application for professional recording) can use it, since it is a plug-in, that is, it is embedded in other applications.